Electrical generators in which all the windings are located in stationary parts are known. Such generators are used especially as interdigited alternators for use with motor vehicle engines. A windingless generator rotor is coupled directly to a shaft to minimize the size and weight of the generator and eliminate brushes or other sliding electrical connections. It is also known to cool these generators with oil from a pressurized oil supply. However, for the generators proposed thus far, the cooling has been insufficient under high performance operating conditions.